Last week she accidently dropped pasta sauce on my new shirt but never apologized and showed no signs of remorse. She expects me do to a lot of stuff for her but I don't get a single thank you after doing them. It could have somthing to do with her culture and how her parents raised her. She is an only child so her parents always coddled her growing up.
Unless she stated explicitly that you just don't deserve it or she shouldn't have to, she may have a completely valid reason for not saying I'm sorry or thank you.
Sometimes, these action feels forced and unnecessary. When we really have messed up, more important to the offended party is to know that we acted unjustly and are not alright with the fact that our actions were unnecessarily harmful to somebody.
If it was an accident, I wouldn't even expect an apology, to be honest.
Though most people would provide one just for the sake courtesy, so I can see why this "bother" you.